Effect of Log Diameter and Clearance Angle on the Peel Quality of 0.125-Inch-Thick Douglas-Fir Veneer

Two-inch wide disks cut from five green Douglas-fir logs were converted to 0.125-inch-thick veneer on an experimental mini-lathe. A constant roller-bar compression of 13 percent was maintained with a freely rotating bar 0.625-inch in diameter. Mean cutting speed was 14.5 feet per minute. The knife had a 23? main bevel angle without microbevelling. Veneer peel quality was determined in terms of thickness uniformity, roughness, lathe-check depth, and lathe-check frequency. Specific gravity appeared to be directly proportional to average veneer thickness and lathe-check frequency. The number of growth rings per inch was negatively correlated with lathe-check depth and veneer roughness. All four peel-quality attributes had an axis of symmetry at 0?00′ clearance angle. A clearance angle of 0?30′ can be recommended for optimizing thickness control from 13-inch to 5-inch diameter. For best control of veneer roughness, clearance angle should increase from 0?00′ at the periphery to 0?30′ in the central heartwood and decrease again to -0?30 near the core. To ensure lathe checks of sufficient depth for good handling characteristics, a clearance angle of 0?00′ to 0?30′ is suggested. Lathe-check frequency will be maximized with 0?00′ clearance angle. Best peel quality was associated with changing rub length on knife face as peeling progressed from sap to core.

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